Tropical Storm TRAMI Advisory 9月22日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 28W (TRAMI)
WARNING NR 05//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 28W (TRAMI), LOCATED APPROXIMATELY 250 NM
NORTHWEST OF ANDERSEN AFB, GUAM, HAS TRACKED WEST-NORTHWESTWARD AT 12
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS A PERSISTENT CENTRAL DENSE OVERCAST (CDO) OBSCURING
THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS
PLACED WITH MEDIUM CONFIDENCE BASED ON THE OBSCURATION OF THE LLCC.
A 211737Z SSMI 89 GHZ MICROWAVE IMAGE PROVIDED ADDITIONAL SUPPORT TO
THE INITIAL POSITION, SHOWING A SMALL CORE WITH DEEP CONVECTION
SURROUNDING THE SYSTEM ON ALL BUT THE SOUTHEASTERN QUADRANT. THE
INITIAL INTENSITY OF 45 KNOTS IS HEDGED HIGHER THAN THE MULTI-AGENCY
DVORAK CURRENT INTENSITY ESTIMATES OF T2.5 (35 KNOTS) BASED ON AN
AUTOMATED DVORAK ESTIMATE OF T3.0 (45 KNOTS) AND A SATCON ESTIMATE
OF 47 KNOTS. TS 28W LIES IN A VERY FAVORABLE ENVIRONMENT, WITH LOW
VWS, ROBUST POLEWARD OUTFLOW AND HIGH SSTS. TS 28W IS TRACKING WEST-
NORTHWESTWARD UNDER THE INFLUENCE OF THE WEST TO EAST ORIENTATED
SUBTROPICAL RIDGE (STR)LOCATED TO THE NORTH.
3. FORECAST REASONING.
A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE. HOWEVER, THE FORECAST
PEAK INTENSITY HAS BEEN LOWERED TO 130 KNOTS AND THE TAU 120
FORECAST INTENSITY HAS BEEN LOWERED TO 120 KNOTS.
B. TS 28W WILL CONTINUE TO TRACK WEST-NORTHWESTWARD THROUGH TAU 72
UNDER THE STEERING INFLUENCE OF THE PREVIOUSLY DISCUSSED STR. ALL
ENVIRONMENTAL FACTORS (VWS, SST AND UPPER-LEVEL OUTFLOW) ARE ALL
HIGHLY FAVORABLE FOR RAPID INTENSIFICATION (RI) THROUGH THE NEXT 48
HOURS, SUPPORTED BY RI-SPECIFIC MODEL GUIDANCE, WHICH ARE INDICATING
A VERY HIGH PROBABILITY OF A SIGNIFICANT RI EVENT IN THE NEAR TERM.
BEYOND TAU 48, THE ENVIRONMENT WILL STILL SUPPORT ADDITIONAL
DEVELOPMENT, THOUGH AT A SLIGHTLY SLOWER RATE, AS OUTFLOW BECOMES
SLIGHTLY LESS ROBUST. DYNAMIC MODEL GUIDANCE IS IN VERY GOOD
AGREEMENT WITH A MODEL SPREAD OF 120NM BY TAU 72. THEREFORE, THERE
IS HIGH CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.
C. AFTER TAU 72, THE FORECAST BECOMES MUCH MORE COMPLEX AND
UNCERTAIN AS THE STEERING PATTERN BEGINS TO BREAK DOWN. BY TAU 96,
THE STEERING RIDGE BECOMES ERODED AND MOVED EASTWARD BY A DEEP MID-
LATITUDE TROUGH APPROACHING FROM THE NORTHWEST. A SECOND STR WILL
DEVELOP BEHIND THE TROUGH OVER CENTRAL CHINA, WITH A LARGE COL AREA
BETWEEN THE STRS, RESULTING IN A WEAK STEERING ENVIRONMENT FOR TS
28W. AS THE SYSTEM ENTERS THIS REGION, IT WILL SLOW SIGNIFICANTLY,
BECOMING NEARLY QUASI-STATIONARY BY TAU 96. ENVIRONMENTAL CONDITIONS
WILL REMAIN FAVORABLE THROUGH TAU 96, ALLOWING TS 28W TO REACH A
PEAK INTENSITY OF 130 KNOTS AT TAU 96. A SLOW WEAKENING TREND IS
FORECAST AFTER THIS POINT, AS THE OHC IN THIS AREA IS RELATIVELY
LOW, AND UPWELLING LEADS TO A REDUCTION IN THE AVAILABLE ENERGY TO
SUPPORT THE SYSTEM, ESPECIALLY AS IT IS FORECAST TO BE QUASI-
STATIONARY IN THIS AREA. DYNAMIC MODEL GUIDANCE IS IN POOR AGREEMENT
WITH A TRACK SPREAD OF 535NM BY TAU 120. CTCI AND JGSI ARE THE
PRIMARY OUTLIERS TO THE NORTHEAST AND SOUTHWEST, RESPECTIVELY, WITH
THE REMAINDER OF THE GUIDANCE SPREAD FAIRLY EQUALLY BETWEEN THE
OUTLIERS. THEREFORE, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE
JTWC FORECAST TRACK WHICH IS PLACED NEAR THE MULTI-MODEL CONSENSUS.
BEYOND THE FORECAST PERIOD, DYNAMIC MODEL GUIDANCE BECOMES EVEN MORE
UNCERTAIN, WITH OVER 900NM SPREAD BETWEEN THE NAVGEM SOLUTION TO THE
WEST OVER COASTAL CHINA, AND THE COAMPS-TC SOLUTION TO THE EAST OF
OKINAWA.//
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